Speech coding system and a method of encoding speech

ABSTRACT

A speech coding system of the code excited linear prediction (CELP) type comprises means (24,26) for filtering digitised speech samples to form perceptually weighted speech samples. Entries in a one-dimensional codebook (110) comprising frame length sequences are filtered in a perceptually weighted synthesis filter (28) to form a one-dimensional filtered codebook (38). The filtered codebook entries are compared with the perceptually weighted speech signals to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesised. Using a one-dimensional codebook (110) reduces the amount of computation which is required compared to using a two-dimensional codebook.



